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Want to Understand Mortality? Look to the Chimps

Pansy was probably in her 50s when she died, which is pretty good for a chimpanzee. She passed in a way most of us would envy — peacefully, with her adult daughter, Rosie, and her best friend, Blossom, by her side. Thirty years earlier, Pansy and Blossom arrived together at the Blair Drummond Safari and Adventure Park near Stirling, Scotland. They raised their children together. Now, as Pansy struggled to breathe, Blossom held her hand and stroked it.

When the scientists at the park realized Pansy’s death was imminent, they turned on video cameras, capturing intimate moments during her last hours as Blossom, Rosie and Blossom’s son, Chippy, groomed her and comforted her as she got weaker. After she passed, the chimps examined the body, inspecting Pansy’s mouth, pulling her arm and leaning their faces close to hers. Blossom sat by Pansy’s body through the night. And when she finally moved away to sleep in a different part of the enclosure, she did so fitfully, waking and repositioning herself dozens more times than was normal. For five days after Pansy’s death, none of the other chimps would sleep on the platform where she died.

This account was published in 2010 in the journal Current Biology, but it’s not the only time scientists have watched chimpanzees, bonobos and other primates deal with death in ways that look strikingly like our own informal rituals of mourning: watching over the dying, cleaning and protecting bodies and displaying outward signs of anxiety. Chimps have been seen to make loud distress calls when a comrade dies. They investigate bodies as if looking for signs of life. There are many cases of mothers refusing to abandon dead infants, carrying and grooming them for days or even weeks. Still, it’s rare to capture primate deaths, especially those of chimpanzees and bonobos, in detail. It happens just often enough that many scientists are starting to think there’s something interesting, maybe protohuman, going on.

But this sort of speculation is laden with epistemological issues: are the scientists guilty of anthropomorphizing their subjects? Are these just isolated events? Are they more likely in captivity? Stories like Pansy’s are mere anecdotes in a world that demands testable hypotheses, and they color the fringes of a continuing scientific debate: Can we find the basis for aspects of our culture in the behavior of other primates?

Earlier this month, the U.S. Fish and Wildlife Service issued a proposal to put captive chimpanzees on the federal endangered species list. (Wild chimps have officially been endangered since 1990.) The goal is to clear up a bureaucratic catch that treats some chimps different from others, but it has big implications for what we can do with the animals — both as medical-research subjects and comic relief on screen. It’s also part of a shift in how we perceive chimps: Are they just animals, or are they something closer to us? Understanding how chimpanzees cope with death is part of that increasing sense of closeness.

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Illustration by Denise Nestor

Brian Hare, an evolutionary anthropologist at Duke University, is convinced that an ape death he witnessed gave him a glimpse into something significant, especially because the animals acted so thoroughly against their own interests. “As a person, I can tell you what it feels like to watch,” says Hare, who describes the experience as emotionally intense. “As a scientist, though, you’re supposed to rely on ideas that can be tested and falsified. And how could you possibly do an ethical experiment here?” Hare studies how chimpanzees and bonobos solve problems, and in 2007 he happened to see one of our closest evolutionary relatives die. He was at a bonobo orphanage in the Democratic Republic of Congo when Lipopo, a newcomer to the orphanage, died unexpectedly from pneumonia. Although the other bonobos could have moved away from his body and traveled anywhere in their very large, heavily forested enclosure, they chose to stay and groom Lipopo’s corpse. When their caretakers arrived to remove the body, the vigil morphed into a tense standoff.

In the video Hare took, Mimi, the group’s alpha female, stands guard over Lipopo’s body. When the caretakers try to push the corpse out of the enclosure with long poles, Mimi fights them, viciously. She grabs the poles with both hands, wrenching them away from Lipopo. She calls to other bonobos, who help her fend off the humans from two sides. Even when the vet arrives with a tranquilizer gun, Mimi stands her ground, her mouth open wide in a scream that’s inaudible in the silent film. Mimi wasn’t related to Lipopo. In fact, she barely knew him, Hare told me. But Mimi was willing to risk an encounter with a gun to protect the body of a mere acquaintance. “That’s why I started to cry,” Hare said. “I don’t know why she did it.”

The results of primate-behavior studies can be humbling for humans because they often call into question our anthropocentric view of the world. Scientists used to say only humans used tools. Then, in 1960, Jane Goodall watched a chimpanzee catch termites using a blade of grass as a lure. A similar watershed moment happened in 1953, when a Japanese macaque named Imo began washing sweet potatoes that scientists gave her. By the 1970s, most of her descendants had learned to do the same. It was a new idea, not shared by all groups of macaques, spread from one monkey to another by social interaction — exactly how scientists define culture.

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Tetsuro Matsuzawa, a primatologist at the Primate Research Institute at Kyoto University in Japan, says that variations in tool use provide an easy way to see that chimps are capable of sustaining a culture over multiple generations. The chimpanzees that Goodall observed in Gombe Stream National Park in Tanzania may use grass to fish for termites, but the group Matzusawa studies in Guinea doesn’t. (They can break open nuts with a pair of rocks, though; Goodall’s didn’t.)

Scientists want to better understand how much of this death behavior is cultural and how much is innate — or if it’s even widespread at all — but that will be rather difficult. Observable deaths don’t happen often, and they don’t happen in quite the same way each time. It’s hard to say definitively what Hare saw: Mimi might have been as protective of anything left in her pen, whether dead body or old sandbag.

Further observation might help us identify the substrate beneath human culture. Take the grooming of the dead, for instance. All human cultures address the cleaning of dead bodies in different ways, Hare says, but all of them do something to cleanse corpses. In fact, compared with most other animals, primates share an inordinate concern for cleanliness, even for those no longer with us. Finding out if this is behavior we share with chimps and bonobos, as it appears to be, could cast a new light on our own funerary rituals and even, perhaps, our notions of purity in the afterlife.

Our understanding of how chimps deal with death may remain limited and speculative, but it hints at the need for a new approach to great-ape conservation. As we’re now poised to end a somewhat arbitrary regulatory distinction between wild and captive chimps, it’s worth considering how we’re protecting actually distinct groups of chimps, some of which may have developed their own cultures. When they die off, they take with them behaviors that we might not find anywhere else and that we don’t yet understand — maybe including, somewhat tragically, the extent to which they comprehend their own demise.

Maggie Koerth-Baker is science editor at BoingBoing.net and author of ‘‘Before the
Lights Go Out,’’ on the future of energy production and consumption.

A version of this article appears in print on June 30, 2013, on Page MM14 of the Sunday Magazine with the headline: Alas, Poor Bonzo. Today's Paper|Subscribe